The Challenges of Robust Inter-Vehicle Communications

Inter-vehicle communication has to be able to cope with adverse conditions like received signal
strength fluctuations, channel load saturation, or high mobility to provide robust communication
services as a basis for safety-related applications. We show the impact of realistic radio models
on the performance of vehicular ad hoc networks. While most of the implications are known,
some of them appear to be underestimated in vehicular scenarios. We want to convince
protocol designers of `thinking in probabilities' when intending to achieve reliable
communications. Among the contributions of this paper are a discussion of link layer
desynchronization, a derivation of probabilities of bidirectional links and associated costs, and
a fairness concept.